Conventional control apparatus of an internal combustion engine is required to output two kinds of signals corresponding to rotation of a crank shaft, for instance, a first signal which is at a high level when the crank shaft reaches top dead center (TDC) and a second signal which is at a high level for every two degrees rotation of the crank shaft, as shown in FIG. 1 of Japanese Patent Publication No. 62-42154 published on Sept. 7, 1987 entitled "Ignition Timing Control Apparatus". Therefore, the prior art requires two sets of pickup elements for detecting the rotation of the crank shaft and one or two sets of rotors for outputting the two kinds of signals.
The prior art of Japanese Patent Publication No. 62-42154 does not consider reduction in the number of parts for producing the above-mentioned signals. Accordingly, the prior art has a drawback that two sets of pickup elements and two sets of rotors for producing two kinds of signals are required as signal sources of the signals outputted according to the rotation of the crank shaft.